Abrasive device



July 20, 1937. c. W. Foss 2,087,318

ABRAS IVE DEVI CE INVENTOR. CARL W. FOS$ BY ATTORNEY.

Patented July 20, 1937 PATENT OFFICE ABRASIVE DEVICE Carl W. Foss,Niagara Falls, N. Y., assignor, by

mesne assignments, to The Carborundum Company, Niagara Falls, N. Y., acorporation of Delaware Application July 8, 1936, Serial No. 89,566

6 Claims.

The present invention relates to abrasive structures, preferably insheet form, and more particularly to the treatment of material for thepurpose of forming 'or attaining'composite structures from which wellknown forms of sheet abrasives may be shaped such as what are commonlyknown as abrasive discs.

The conventional practice of abrading irregular surfaces such asautomobile bodies includes 10 the use of an abrasive disc combined witha flexible supporting pad of a diameter complementary to that of thedisc. Such an assembly is usually driven by means of a flexible shaft sothat the abrasive may be manually moved over the surface of the workunder treatment. The rotating flexible pad provides a support for theabrasive disc and also permits the disc attached to the center thereofto flex laterally and follow the contour of an irregular work surface.By reason of the flexible nature of the arrangement only a relativelysmall portion of the disc, namely the peripheral surface thereof, isbrought into contact with the work surface. The useful portion of therevolving disc is therefore a com- 5 paratively narrow annulus varyingin width from the peripheral edge towards the center of the disc inaccordance with the flexibility of the combined assembly and thepressure applied by the operator. The general type of such disc isapproximately nine inches in diameter and the annulus or useful portionvaries from inch to 1 /2 inches as measured radially inward from theperipheral edge. After the abrasive particles carried by this portion ofthe disc become dull or worn away the disc is no longer useful and mustbe discarded in favor of a new disc.

It is therefore an object of the present invention to provide a disc andsupporting pad combination with such structural characteristics as willpermit a greater portion of the abrasive surface of the disc to beutilized than has been heretofore possible.

A more specific object of the invention is the .provision of asupporting pad with a diameter appreciably less than that of the discand combining an abrasive disc therewith of such a ing that isrelatively rigid as compared to previousdiscs of this general type sothat grinding pressure will be obtained by the peripheral portion shownin Figure 2 after the Worn edge has been thereof when the same isassociated with a supporting pad of an appreciably smaller size.

Other and further features and objects of the invention will be moreapparent to those skilled in the art upon a consideration of the accom-5 panying drawing and the following description wherein an exemplaryembodiment of the invention is disclosed. I

Figure 1 is a view in side elevation of an abrasive disc and supportingpad. 10

Figure 2 is a view of an abrasive disc showing the relatively narrowannulus of the face with the abrasive particles removed as a result ofengagement of that portion of the disc with a Work surface. 15

Figure 3 is a side plan view of the assembly showing the manner by whichthe worn annulus of the disc may be sheared.

Figure 4 is a face view of the abrasive disc removed.

Referring to the drawing there is represented in Figure l a flexiblesupporting pad ll of a smaller diameter than that of the conventionaltype of abrasive support. That is to say, the present inventioncontemplates a smaller disklike pad than that heretofore employed asexemplified in U. S. Patents Nos. 1,686,898 and 1,686,938 hereinafterreferred to or if the old type of flexible pad is employed the diameterof 0 the abrasive disc is such that an inch or more of the abrasiveextends beyond the periphery of the pad. A pad of such dimension ascompared to the diameter of the disc and otherwise similar to pads ofthe prior art may be rotated in the usual manner by attaching the hub l2to an appropriately driven flexible shaft (not shown) so that theabrasive disc I3 attached at its center and supported in front of theDad ll may be moved over a work surface such as represented at 14.

After the disc l3 has been used a portion of the abrasive particlesbecomes dull or is entirely removed from the face of the disc asillustrated in Figure 2 by the annulus IS. The differential in size ofthe yieldable pad H as compared to that of the disc I3 is provided forthe purpose of permitting the worn annular portion thereof to be shearedby forcing the edge H of the rotating disc into engagement with the worksurface as indicated in Figure 3. r

In carrying out a grinding operation with such an assembly wherein theabrasive disc is materially larger than the supporting pad it is neces-I sary to provide the disc with structural characteristics which willcause the portion l8 of the disc extending beyond the pad to maintaingrinding contact with the work surface when lateral pressure is appliedby the operator. The backing for the abrasive particles must thereforebe more rigid than any of the structures of the prior art, particularlymore so than those disclosed in Patents Nos. 1,686,898 and 1,686,938issued respectively to Richard P. Carlton and Herbert R. Stratford,since the supplementary backing or pad does not extend to support theentire disc. In addition to rigidity the backing must also be yieldableenough to permit the abrasive particles to follow irregularities in thework surface.

In the fabrication of abrasive sheet material from which discs of suchcharacteristics may be shaped a sheet of fabric, for example, textilecloth known as Ohio Falls preshrunk drill weighing about 2.5 pounds perrunning yard and approximately 28 inches wide is treated by applying aliquid, heat-hardenable resin such as a phenol aldehyde condensationproduct to one face thereof in the ratio 10 pounds of liquid to a (480sheet 9 x 11) ream of cloth. After the fabric has been so treated thevolatile liquids of the resin may be driven off by heating the materialfor a period of two hours at a temperature which will not cure the resinto any appreciable extent and preferably in a range between to F.

Abrasive particles are adhesively attached to one face of the fabric ashereinafter described and in order that a matrix will be provided tostiffen and strengthen the threads of the cloth and insure uniformshearing of the fibers of the cloth while the fabric is being cut downit is essential that the cloth be supported by a.highly rigidreinforcement such as filling the interstices or voids between thethreads of the cloth and the fibers thereof with some relativelyinflexible material. It is for this purpose that the opposite face ofthe fabric is then treated with a quantity of the above indicated resinsufficient to fulfill the above requirements and preferably in theamount of 8 pounds per ream. After the application of the second coatingthe fabric may be permitted to dry or it may be ,festooned and dried byheating at a temperature which will not materially cure the resin andspecifically between 165, and 170 F.

' Any tough ductile material such as fish paper may be employed as abase for the fabric and hydrated cellulosic material or vulcanized fiberhas been found to be satisfactory for this purpose. A sheet of suchmaterial having a thickness of substantially .010 inch and a widthcomplementary to that of the fabric is coated with a phenol aldehydecondensation product resin in the ratio of approximately 6 pounds perream. After one face of the fiber is thus coated the fabric or cloth asabove treated may be united therewith by rolling the two sheets at roomtemperature to adhesively join the same. As a result of the rollingoperation a portion of the resin with which the fiber has been coated isabsorbed by the fabric to further fill the fibers and intersticesthereof.

Preparatory to applying the abrasive particles the fabric face ofcomposited material, formed in accordance with the hereinabove describedmethod, should be coated with sufficient resin to affix a layer ofabrasive grain thereto. cloth face of a ream of the composite sheet maybe treated with 22 pounds of a resin derived from mixing a liquid phenolaldehyde condensation product with a powdered A stage heat-hardenablephenolic resin. Various proportions of the liquid and solid resins maybe combined and 100 pounds of the powder mixed with 500 pounds of liquidhas been found to provide a suitable adhesive for the abrasive particlesand further fill the fibers or threads of the fabric. Thereafter 95pounds of abrasive particles, as for example fused alumina, is spreaduniformly over the fabric face of a ream of the composite material. Asizing coat of the same mixture of resin is then applied in an amount toproperly affix the abrasive particles to the fabric and 18 pounds ofsuch a resin per ream has been found to fulfill these requirements.

Thereafter the material should be festooned and dried for a period of 10hours at approximately 125 F. and '7 hours at a temperature of F. afterwhich the same may be rolled to impart a small curvature to thecomposite sheet material. The resin of the rolled sheet is then cured ata temperature of 250 F. for a period of 16 hours. It will be apparenthowever that time and temperature required to properly cure the resinmay be varied in accordance with the particular resin employed. Theselatter temperatures cure all of the resin which has been employed inconnection with the fabricincluding the coats employed to adhesivelyjoin the fabric and the fiber, together with the grain securingapplications.

Discs such as illustrated in Figure 1 may then be cut from the sheetmaterial comprising a layer of abrasive particles which are supported bya composite backing consisting of a fabric sheet coated with a resin tosuch an extent that the cloth is brittle and a fiber sheet of toughductile cellulosic material to render the structure rigid and onlyslightly flexible so that if the same is bent beyond the flexureincident to the grinding operation or beyond the elastic limit thereofcracks develop in the cloth as distinguished from previous clothcombinations wherein the bond stretches or bends to maintain thecontinuity" under considerably more fiexure.

A disc formed in accordance with the hereinabove method may therefore beoperated in connection with a supporting pad having a smaller diameterthan the abrasive. The rigid character of the composite backing impartssufficient stability to the disc to maintain grinding by the faceadjacent the periphery under pressure of the operator. The disc may beused in such a. manner until the abrasive particles are dull or flakedaway to form a relatively barren portion as indicated by the annulus inFigure 2. The assembly being free for movement by reason of the flexibleshaft may then be positioned in such a manner that the edge I! of thedisc is brought into engagement with a protuberance in the work surfaceas illustrated in Fig e 3 when the fabric is sheared uniformly to re methe diameter of the disc. Such operation of the disc does not alwayscause the fiber sheet to be sheared since it is tough and ductile. Itappears that the fiber first curls towards the supporting pad in amanner such as indicated in Figure 3. Continued engagement of the edgeof the rotating disc with a projection in the work surface causes thecurled fiber to be abraded or worn so that the diameter is substantiallyequal to that of the sheared fabric at the end of the cutting operation.

Although certain steps have been described as illustrative of a methodof carrying out the invention it will be apparent that modifications maybe made by those skilled in the art. Such modifications may be madewithout departing from the spirit and scope of the invention as setforth in the appended claims.

I claim:

1. A flexible abrasive article comprising a composite backing consistingof a cellulosic sheet, a fabric sheet adhesively attached to one face ofsaid cellulosic sheet, and a heat-hardened resin intermingled with thefibers of said fabric in a quantity sufficient to provide the same witha relatively brittle characteristic and a layer of abrasive particlesadhesively attached to the face of said fabric.

2. A flexibleabrasive article comprising a composite backing consistingof a hydrated cellulose sheet, a fabric sheet adhesively attached to oneface of said cellulose sheet, and a heat-hardened resin filling theinterstices of said fabric sheet in a quantity sufficient to provide thefabric component of said backing with a relatively rigid brittlecharacteristic and a layer of abrasive particles adhesively attached tothe face of said fabric.

3. A flexible abrasive article comprising a composite backing consistingof a vulcanized fiber sheet, a fabric sheet adhesively attached to oneface of said fiber sheet, and a heat-hardened resin intermingled withthe threads of said fabric and filling the interstices thereof in aquantity sufficient to provide the fabric with a shearablecharacteristic and a layer of abrasive particles attached to the fabricface of said backing.

4. A flexible abrasive comprising a composite backing consisting of avulcanized fiber disc, a

textile fabric disc adhesively attached to one face of said fiber disc,a heat-hardened phenol aldehyde condensation product resin surroundingthe threads and filling the voids of said textile fabric to reinforcethe fabric and render the same brittle whereby the same will shearuniformly when the peripheral edge thereof is applied to the worksurface and a layer of abrasive particles attached to the fabric face ofsaid backing.

5. A grinding device comprising the combination of a flexible disc-likesupporting pad, with a flexible abrasive disc of a larger diameter thanthat of said pad having a composite backing consisting of a vulcanizedfiber disc combined with a brittle fabric disc carrying abrasiveparticles whereby the abrasive disc will maintain itself beyond theperiphery of said pad to provide grinding by the portion of the discextending beyond said pad and the fabric component of such portion maybe sheared when the edge thereof is applied to the work surface.

6. A grinding device comp-rising the combination of a flexible disc-likesupporting pad with a flexible abrasive disc, the said abrasive discbeing of materially greater diameter than that of said pad and having acomposite backing, consisting of a cellulosic sheet characterized bytoughness, flexibility, and high resistance to buckling combined with abrittle fabric sheet carrying abrasive particles whereby the saidabrasive disc will be self-supporting beyond the periphery of said padto provide grinding by that portion of the disc extending beyond saidpad and whereby the fabric component of such portion may be sheared whenthe edge thereof is applied to a work surface.

CARL W. FOSS.

D l S C L A I M E R 2,087,318.Carl W. Foss, Niagara Falls, N. Y.ABRASIVE DEVICE. Patent dated July 20, 1937. Disclaimer filed May 22,1942, by the assignee, The Oarbo-rumlum Company. Hereby disclaims thesubject matter of claims 1, 2, 3, and 4 of said Letters Patent.

[Ofiicial Gazette June 16, 1942.]

D l S C L A l M E R 2,087,318.Carl W. Foss, Niagara Falls, N. Y.ABRASIVE DEVICE. Patent dated July 20, 1937. Disclaimer filed May 22,1942, by the assignee, The

Oarborundum Company. Hereby disclaims the subject matter of claims 1, 2,3, and 4 of said Letters Patent.

[Ofiic'ial Gazette June 16, 1.942.]

